The effect of polymer concentrations on some of the physicochemical
properties of
Vernonia amygdalina
(Linn) and
Garcinia kola
(Heckel) extracts loaded
microspheres was evaluated. Microspheres of the aqueous extracts was prepared by emulsion
solvent evaporation using polyethylene glycol (PEG) mixtures of molecular weight 4000 and
6000 at different ratios of 1:0, 0:1, 1:1, 1:2 and 2:1 while the amounts of the extracts
incorporated was constant for all ratios. The microspheres were evaluated for their particles
sizes, yield, flavonoid content, loading efficiency, moisture loss and flow properties.
In-vitro
release studies were carried out by monitoring flavonoid release rate from the microspheres.
The microspheres were spherical and uniformly shaped and exhibited good flow
characteristics. Their size range, yield, loading efficiency, moisture loss and flavonoid content
were 76 - 83 μm, 49 - 76 %, 47 - 82 %, 2.18 - 4.60 % and 17.10 - 23.80 mg%, respectively
for
V. amygdalina and 144 - 160 μm, 50 - 68 %, 51 - 68 %, 3.00 - 4.41 % and 20.00 - 28.70
mg%, respectively for
G. kola. Flavonoids release from the microsphere was up to 90 %
within 1 h and it followed a matrix release kinetic model with a super case-II transport
mechanism. The concentrations of the polymers affected the yield, loading efficiency,
moisture loss and the extent of flavonoid release of the microspheres but had no effect on
their particle sizes and flavonoid content. These results may find useful application in the
delivery of
V. amygdalina and
G. kola extracts since the combination of PEG of different
molecular weights resulted in microspheres with good physicochemical and release
properties.
